This invention relates to fluid handling and more particularly to dispensing or proportioning apparatus, namely anti-backflow proportioners known as air gap eductors.
In the past, it has been common to dispense concentrated chemical fluids by sucking them up through a venturi into a water stream and dispensing a flow of mixed water and chemicals. Mixers known as eductors accomplish this task by providing a water flow through a venturi section and sucking chemicals into the flow through a low pressure orifice in the venturi section. Such eductors are useful in a number of applications, such as in dispensing diluted cleaning agents for cleaning procedures.
In these systems, it is important to maintain the water source free of contamination so that chemicals are not drawn back into the water source. This has been accomplished through the use of backflow preventors such as air gap eductors. In essence, such air gap eductors include a nozzle upstream of the venturi section for defining a stream of water flowing across an unobstructed gap in the eductor body prior to entering the venturi section. Upon any water shut down or pressure reversal in the water system, the water stream terminates, leaving a gap in the eductor between the nozzle and the venturi section where the chemical is otherwise first introduced. There is thus no mechanism capable of transmitting chemical back to the nozzle or upstream in the water supply. Typically, the eductor body is provided with open (or baffled) windows in the gap area to accommodate and pass any water overspray during operation.
Forms of air gap eductors are disclosed, for example, in U.S. Pat. Nos. 5,519,958; 5,522,419 and 5,253,677 specifically and expressly incorporated herein by reference.
While certain of the former air gap eductors have proven very useful, such eductors still have room for improvement. For example, it is desirable to minimize and eliminate overspray and misting in the air gap section to obtain a drier, less messy operating environment.
Many factors may contribute to such overspray. One factor is the dynamic of the water stream as it enters the venturi section. Since it is generally considered desirable to overdrive the venturi, that is to direct more water into the venturi than can flow therethrough, some portion of the water stream never flows into and through the venturi, but rather flows around its outside structure as overflow, back splash, droplets, spray, mist or the like. It is desirable to control this overflow and to minimize or reduce its flow back into the air gap area or chamber.
Also, it is important to maintain alignment of the water stream from the nozzle into the venturi opening. If the stream is misaligned, overspray greatly increases, causing too much splashing, back spatter and misting. Such misalignment may be caused, for example, by any undesirable flexation of the eductor body structure between the nozzle and the venturi section. Such flexation may be caused, for example, by manipulation of the discharge hose extending from the eductor. Accordingly, it is desirable to provide an eductor body sufficiently rigid to prevent water stream misalignment.
Also, it is noted that the overspray discharge of certain eductors generally surrounds the primary mix discharge and includes air. When discharged into the same receptacle, such as a bucket, for example, this aerated overspray discharge causes undesirable foaming. It is thus desirable to reduce or eliminate foaming due to turbulent overspray discharge.
In another aspect of air gap eductors, various governmental authorities or certifying agencies have developed codes or standards for air gap eductors. A typical standard is the rquirement that the air gap between the upstream nozzle and the venturi be at least one inch (i.e. 2.54 centimeters) in length, and that the distance from the nozzle orifice to the interior surface of the eductor body be at least four times the diameter of the nozzle orifice.
In yet another aspect of the invention, it is noted many prior eductors require numerous parts, raising their costs and their assembly expense. It is desirable to provide an air gap eductor meeting significant code limitations, reducing or eliminating overspray, backsplash and foaming, and at the same time of few parts.
It is thus one objective of the invention to provide an improved air gap eductor which minimizes or eliminates misting, overspray, backsplashing and the like into the air gap chamber.
Another objective of the invention has been to provide an improved air gap eductor with reduced foaming discharge.
Another objective of the invention is to provide an improved air gap eductor with reduced overspray and reduced foaming discharge while retaining an air gap over one inch between water nozzle and venturi entry and a distance of four times the nozzle orifice diameter between the nozzle orifice and internal surfaces of the eductor body.
Another objective of the invention is to provide an improved air gap eductor of molded configuration of only three separate body parts.
A further objective of the invention has been to provide an improved overspray and misting shield for an air gap eductor.
To these ends, an eductor according to a preferred embodiment of the invention includes an integrally molded eductor body, a nozzle fitting in the body and an overspray shield fitting over an integrally molded venturi section in the body. The nozzle fits within the body at a water inlet end to define a water stream. The shield fits into the body at the downstream end of an air gap chamber defined by the body and is of a construction to cooperate with the venturi section to control overspray and backsplash. In particular, the shield is of frustoconical configuration fitting over a tapered inlet end of the venturi section. The shield has a plurality of parallel spray deflecting rods extending outwardly toward interior eductor wall surfaces and is positioned by four spider-like arms within the body. A conical skirt of the shield extends around the venturi inlet and has a V-shaped cut to accommodate the integral portion of the venturi's attachment or projection from the eductor body. The upstream interior surface of the conical skirt just at the venturi inlet terminates at a shoulder useful for preventing backsplash.
The venturi inlet is formed in a venturi section projection from the eductor body and is defined in part by two diverging walls and a conical surface therebetween, with the skirt of the shield overlying these surfaces. The venturi inlet is an open bore centered on the knife edge. This edge cleanly cuts the stream of water from the air gap chamber into a main venturi stream and a bypass stream, resulting in a bypass stream of significant velocity and momentum. This improves the flow around the venturi minimizing turbulence and misting or droplets moving upstream. Overflow water or spray not entering the venturi is captured by the shield, tends to form a water sheet thereon and eventually flows downstream capturing ambient mist or droplets. Mist generated by the turbulence of the venturi entry and exiting the shield generally flows downstream. Any mist tending to flow upstream outside the shield collects on the rods and eventually flows downstream into the discharge.
The clearances between the skirt and the venturi section are minimal, as shown in the drawings, to handle overspray while open areas around the outside of the shield and interior of the eductor body provide sufficient venting to allow overspray to flow downstream but without undue foaming in any discharge receptacle.
Such construction permits the efficient use of relatively large venturi passages as compared with past units and the efficient mixing and discharge at high flow rates of 4 to 6 gallons per minute, for example. More chemical flow is thus provided.
Accordingly, the preferred embodiment of the invention reduces or eliminates back splashing and misting, improves the discharge quality and provides an improved air gap eductor of few parts and less expensive integrally molded features.
These and other advantages will be readily apparent from the following detailed description of a preferred embodiiment and from the drawings in which: